Cables, i.e. two or more wires within a single covering, a wiring harness, i.e. an assembly of discrete insulated wires, have long been used to interconnect the various components of electrical systems.
Typically, cables require testing after fabrication to ensure continuity between terminal positions at opposite ends of the cable. However, a continuity check with a multimeter for a 36 pin to a 36 pin cable with an unknown pinout would require checking about 2500 connections by hand.
A variety of equipment is known for determining interconnections between terminal positions at opposite ends of the cable. U.S. Pat. No. 4,620,282 to Shelley discloses a stand alone cable tester comprising a microprocessor-based tester unit, visual display, printer interface, power supply and test adapters. A printer is provided for documenting the pinout. The device of U.S. Pat. No. 4,620,282 uses customized printer circuit boards for changing connector types. Further, cable signatures and adapter signatures are generated in order to assign unique descriptions to the test cable and adapters required for interfacing the cable to the tester. The adapter signatures are generated by interpretation of hard-wired pins on the printed circuit adapter boards. The cable signature is generated by using an algorithm to assign a unique reference identification to a cable pinout. There is no provision provided for permanently storing the cable pinout for later access in a file or memory, the cable signatures must be compared in order to find discrepancies. The device of U.S. Pat. No. 4,620,282 outputs a test signal to a given test point or pin by means of a demultiplexer integrated circuit chip. The status of each other point or pin under test is then read by the tester while the test signal is still being applied by means of a multiplexer. This testing procedure requires separate multiplexing and demultiplexing components.
U.S. Pat. No. 4,257,002 to Helms et al discloses a stand alone microprocessor based cable tester for comparing the pinout of a known harness to that of an unknown harness. The conditions of the known good harness is stored on cassette tape, and are later input back into the internal memory. The device of U.S. Pat. No. 4,257,002 only determines whether an unknown cable is identical to that of a known cable or that of the information stored in its memory, but does not provide any information as to the pinout of the cable. U.S. Pat. No. 4,257,002 uses a separate IC for inputting and outputting data.
U.S. Pat. No. 4,218,745 is directed to a harness fabrication and testing device. This device uses a separate integrated circuit for input and output signals, which allows testing while the test signal is still being applied. The device of U.S. Pat. No. 4,218,745 requires autoplexed transponders to connect the harness to the computer.